Mercury cathode electrolysis cell



y 0, 1969 J. SCHUCKER ETAL 3,445,373

I MERCURY CATHODE ELECTROLYSIS CELL Filed Nov. 14, 1966 MR mm 2 w N C T w uSrL ME ammjw NU c.2\ W E L m JWW BY Q United States Patent MERCURY CATHODE ELECTROLYSIS CELL Josef Schiicker, Saarlandstr. 3; Franz Glos, Kaiserstrasse 43; and Willi Nemetz, Am Zehnthof 19, all of 46 Dortmund, Germany Filed Nov. 14, 1966, Ser. No. 593,791 Int. Cl. C22d N04 US. Cl. 204-219 4 Claims The invention refers to an electrolysis cell with consumable anodes, particularly for the production of alkali hydroxides and chlorine with a mercury cathode.

Electrolysis cells of the type described above can be formed in a known manner of a trough shaped container, in which the mercury serving as the cathode flows along the bottom of the trough, while the anodes, consisting for instance of graphite, protrude into the trough from above. The aqueous solution of the alkali salt, for instance NaCl flows in the same direction of flow as the cathode, between cathode and anode, and is subjected to electrolysis. The halogen evolved during electrolysis is drawn off from the space formed between the electrolyte and the cell cover, while the free metal is bound to the mercury as amalgam and flows oil? with it.

As the free halogen absorbs part of the water contained in the electrolyte, it has highly corrosive properties. For this reason the walls of the cells, but primarily the cover of the cells are given such treatment that they cannot be attacked by the halogen.

If the anodes used in the electrolysis are liable to be consumed, a possibility of adjustment has to be provided. This adjustment can be carried out either individually for each anode or in groups, or, by common adjustment of all anodes of one cell. Therefore, in using solid cell covers provided with a protective layer on its under side, the anodes are brought through this cover in slides, or, attached rigidly to the cover if the possibility of individual adjustment is not required.

In US. Patent No. 2,998,374 it has been proposed to cover the entire cell with a stretched plastic foil impermeable to gas, this foil being clamped tightly not only to the side walls of the cells but also to the individual anodes. This foil is provided with openings to let the connecting parts of the individual anodes pass. According to US. Patent No. 2,627,501 the gap between the anode connections and the cell cover is maintained gas tight by elastic cuffs.

It is the purpose of the invention to create an electrolysis cell which will give a higher output than known cells of this kind, but which in its construction is simplified as much as possible.

It has been found that it is possible to achieve a safe enclosure of the space inside the cell against the atmosphere without a special cell cover, by making the anode plates themselves act as cell cover and making the connections between these anode plates, such as between the anode plates and the cell housing by elastic membranes of rubber or corrosion resistant and gas impermeable plastic material as is known to the art. At the same time a metallic covering is aflixed to the upper side of the anode plates which prevents difiusion of the chlorine through the anode plates and at the same time serves as current supply lead. In case this metal plate does not consist of chlorine resistant material, the anode can be treated to become impermeable to gas.

The electrolysis cell, as disclosed in the invention, consists essentially of a trough, as already used until now in electrolysis cells. The side boards of this trough in their upper part are shaped into a channel which on one side contains a pipe provided with apertures, through which fresh brine is introduced into the cell and distributed.

Between the side channel and the inner space proper of the cell a separating wall is carried to a certain height like a weir, so that the brine flowing from the distributor pipe, flows uniformly over this weir into the inner cell space. The brine flows therefore transversely across the direction of flow of the mercury cathode and is collected in the side channel provided on the opposite side and thence carried olf. A metal plate is attached onto the upper side of each graphite anode, the dimensions of this plate corresponding approximately to those of the graphite anode. The supply of the current is delivered directly to this metal plate from which it is distributed uniformly onto the entire anode surface. Also attached to the metal plate are the connecting members for the support means of the anodes.

The execution of the cell as per concept of this invention makes the use of a special cell cover superfluous, as the anodes themselves close off the cell in the upward direction. The seal between the side boards of the cell and the anodes, as well as between the individual anode blocks is achieved by means of an attack resistant flexible foil of a type known in the art.

The use of this cell as per this invention, as against previously known constructions, results among others in the following advantages:

(1) Apart from the fact that omission of a separate cell cover simplifies the construction greatly, the current distribution from the current supply points to the anodes occurs more uniformly and with a noticeably lower voltage drop as heretofore.

(2) On account of the transverse flow of the 'brine with respect to the mercury cathode, the brine concentration is reduced less with customary loads than in the case of parallel flow of brine and cathode. It is therefore possible to operate the cell at very high loads.

(3) The current consumption is lower than with presently known constructions.

One form of construction of the electrolysis cell in accordance with the invention will be described as an example in the following with the aid of the accompanying drawing which is an elevation partly in section of an electrolysis cell.

The electrolysis cell 1 is built onto a support structure 2 which, through insulators 5 is connected with a base 6. On the support structure 2 rests a cell bottom 11 to which are attached side boards 3. The side boards are disposed in the direction of the longitudinal axis of the cell and form channels 8 and 9. The channel 8 contains a pipe 14, which is provided with apertures distributed along its length and serves for the supply of brine. The brine flows over the weir 18 through the inner space of the cell to the collecting channel 9. From there it is drawn off in the usual manner. On the upper part of an anode block 10 arranged above the cell bottom 11 is attached a cover plate 12, which is connected by bolts 13 to a support structure 4. The depth or up and down positioning of the anodes is effected by means of the adjusting device 7 in the form of a screw threaded rod having a hand wheel and an internally thread sleeve on the support structure 4 and engaging such rod. The inner cell space is sealed from the atmosphere by means of a flexible, attack resistant foil 19 connected respectively to the side boards 3 and the anode block 10.

We claim:

1. An electrolysis cell for the production of chlorine and alkali hydroxides by means of graphite anodes and a mercury cathode comprising a support, a cell bottom on said support, a side board arrangement at opposite sides of and spaced from said cell bottom providing channels, anode block means disposed above said cell bottom, means for delivering electrical potential to said anode block means, said last means including a metal plate on said anode block means, a mercury cathode in said channel, and a flexible sheet membrane between said anode block means and said side board arrangement thereby to seal said anode block means from the atmosphere.

2. An electrolysis cell as claimed in claim 1 comprising means in one channel extending throughout its length for the distribution of fresh brine which flows transversely to the direction of flow of the mercury cathode to the other channel from which the used brine is collected.

3. An electrolysis cell as claimed in claim 2 in which said brine distribution means comprises an apertured pipe, and a weir adjacent said pipe enables uniform flow of brine to said anode block means.

4. An electrolysis cell as claimed in claim 3 comprising means for raising and lowering said anode block means.

References Cited UNITED STATES PATENTS HOWARD S. WILLIAMS, Primary Examiner. 10 D. R. VALENTINE, Assistant Examiner.

U8. Cl. X.R. 

1. AN ELECTROLYSIS CELL FOR THE PRODUCTION OF CHLORINE AND ALKALI HYDROXIDES BY MEANS OF GRAPHITE ANODES AND A MERCURY CATHODE COMPRISING A SUPPORT, A CELL BOTTOM ON SAID SUPPORT, A SIDE BOARD ARRANGEMENT AT OPPOSITE SIDES OF AND SPACED FROM SAID CELL BOTTOM PROVIDING CHANNELS, ANODE BLOCK MEANS DISPOSED ABOVE SAID CELL BOTTOM, MEANS FOR DELIVERING ELECTRICAL POTENTIAL TO SAID ANODE BLOCK MEANS, SAID LAST MEANS INCLUDING A METAL PLATE ON SAID ANODE BLOCK MEANS, A MERCURY CATHODE IN SAID CHANNEL, AND A FLEXIBLE SHEET MEMBRANE BETWEEN SAID ANODE BLOCK MEANS AND SAID SIDE BOARD ARRANGEMENT THEREBY TO SEAL SAID ANODE BLOCK MEANS FROM THE ATMOSPHERE. 